acid_k2
What you are refering to is not a general requirement for european codes.
It is one of the protection and safety measures permited by them.
General tittle of this measure:Electrical isolation (Galvanic Isolation) and is under IEC 364 paragraph 413.5
Again, the IEC 364 is the "blueprint" of all the European applicable codes.
CENELEC has issued the Conformance Document HD 384, which every European Goverment has to adopt by issuing a National Code that will fully comply with the IEC 364.
I would like to stress the fact that this kind of connection is restricted to certain physical locations, certain usages and
accompanied by certain requirements (the most important which you described).
This is exactly the same topic I described in post#18.
Regards
George
What you are refering to is not a general requirement for european codes.
It is one of the protection and safety measures permited by them.
General tittle of this measure:Electrical isolation (Galvanic Isolation) and is under IEC 364 paragraph 413.5
Again, the IEC 364 is the "blueprint" of all the European applicable codes.
CENELEC has issued the Conformance Document HD 384, which every European Goverment has to adopt by issuing a National Code that will fully comply with the IEC 364.
I would like to stress the fact that this kind of connection is restricted to certain physical locations, certain usages and
accompanied by certain requirements (the most important which you described).
This is exactly the same topic I described in post#18.
Regards
George
poogie:
touching something that is earthed at the same time is not a problem. No electric shock.
Where I live, I cannot connect earth to neutral at the service panel. I must connect all earth (equipotential connections) to the house earth system. Neutral is connected to earth only in high-voltage trasformer box of the grid.
gpapag:
you are right.
But the national translation of IEC 60364 I have (CEI 64-8), at the paragraphs 413.5.2 and 413.5.3.1, said: you can't connect the chassis of separated circuit at normal earth system. It's allowed to connect it to a separated earth point.
At the end of this interesting thread:
are we speaking about an isolation transformer? yes
are we speaking about electical isolation, or galvanic isolation (safety measure for preventing electric shock during an earth fault)?
if you connect chassis to earth equipotential connection: no;
if you don't connect it, or at least you connect it at a separate earth point, yes.
But if you connect it to earth, and so there isn't electrical isolation, a controller of isolation is required (correct me if I'm wrong).
touching something that is earthed at the same time is not a problem. No electric shock.
Where I live, I cannot connect earth to neutral at the service panel. I must connect all earth (equipotential connections) to the house earth system. Neutral is connected to earth only in high-voltage trasformer box of the grid.
gpapag:
you are right.
But the national translation of IEC 60364 I have (CEI 64-8), at the paragraphs 413.5.2 and 413.5.3.1, said: you can't connect the chassis of separated circuit at normal earth system. It's allowed to connect it to a separated earth point.
At the end of this interesting thread:
are we speaking about an isolation transformer? yes
are we speaking about electical isolation, or galvanic isolation (safety measure for preventing electric shock during an earth fault)?
if you connect chassis to earth equipotential connection: no;
if you don't connect it, or at least you connect it at a separate earth point, yes.
But if you connect it to earth, and so there isn't electrical isolation, a controller of isolation is required (correct me if I'm wrong).
pooge said:
There are a number of reasons to use 1:1 transformer most are not for power distribution ie voltage conversion in a fixed construction. The main purpose (besides floating an AC DUT in a lab environment ) is for noise reduction and having the ability to get off a noisy ground. This requirement was the driver for a whole market of "extreme" isolation transformers. To get the best common mode reduction is having the ability to break up ground loops in a specific system. When you ground a secondary to earth you have eliminated the common mode by definition. But the common mode noise does not disappear by majick, it gets converted to transverse noise which is even more difficult to filter. The place to put the earth ground is after the last transformer in a system and that is usually not at the secondary of an extreme isolation transformer. This is a system level approach to a noise reduction problem. An electrician is not the go-to guy (expert) when you want solve these type of questions. This has been done before (TEMPEST and other qualified RF screen rooms) and is not breaking the law or a shock hazard when done properly.
Yet you say:
Please clarify if/how you differ from IEEE.
Common mode noise (from the primary system) is removed by the use of two fundamental means: breaking the ground loop and shunting common mode noise to earth by means of the e-shield. The fact that one is required to bond the secondary does not defeat the common mode immunity. Ultra-isolation transformers are no different, they are simply trading off additional guarding of the winding for leakage reactance.
Once the secondary is grounded, there is the potential for common mode noise to enter by the secondary conductors/system, not from the primary. For this reason it is recommended to bond as close to the sensitive load as possible, or even to pursue balanced power. But IEEE's best design (Figure 9-2) still has the secondary bonded per NEC requirements.
But those are not residential users.....
The "noisy ground" issue is a poor argument IMO. A good solution for a problematic ground grid is to improve the electrode system to the earth. Once this is properly established, robust single point grounding of all audio components should be sufficient. Isolated grounding means could be pursued to reduce the effects from nearby equipment. In fact, typical residences built with NM wire, with an audio system on a dedicated branch circuit, already ARE IG:
Your recommendations are not disputed, your application is. Your isolating suggestions are properly and legally applied with the transformers inside the equipment, not external.
zigzagflux said:
That agrees with my statements almost exactly ie "bond as close to the sensitive load as possible including conversion of common mode to transverse mode. By definition means when the reference (earth ground) is connected to a winding you no longer have a differential measurement. Alternately saying - It's now a 2 wire not 3 wire system. I don' know if the IEEE has fixed solution from a general diagram without knowing what the application is and what the specifications are. Not sure maybe it's good enough for what you want/need, but surely not the best.
zigzagflux said:
Those are just two examples of the highest traceable requirements for powerline isolation and noise I could think of. Their application and techniques could be filtered or watered down for less stringent applications.
Noisy grounds are real! If you don't know this I'm not sure what to tell you. There are industries that thrive on the fact.
I'm not saying what the application and specifications are. You tell me. All I know that without a fixed installation (perhaps called a movable appliance?), many of the codes you site are invalid.
well ....
sakis from east electronics informed me about this post and as his employe but also electrics engineer of the NTUA ( National Technical University of Athens )
i try to follow all the posts but is very strange that so many various opinions about the same issue and diferent aspects depending on the standards and the application ....
to me more or less makes no sense ....
many things are said here and some of them quiet strange i dlike to say ....
just a couple of things .....
audio systems ( maybe others like medical systems or tools or dut in a lab ) cannot be faced as electrical loads like other electrical loads like a bulb or a radiator ....
as sakis said there might be earth loops inside our home while we give power to a lighting system but those will not create audible noises ( or the noises created can not be herd)
the other thing is that you cannot treat audio systems with cortizone IE trying to supress noises or other related issues . you simply have to find what picks them up .......
to my opinion if our friend george had noise issues i would go for a solution like double T mains filters than an isolation trafo ... ( but thats my opinion ....only )
PS
sakis and me in our young times (18-20years old and some 20 years ago ) used to make a hell of a lot of money selling to clubs dimmers that produced zero noises to the audio system .....we produced a dimmer that had probabaly 5-6 componeds and was a hell of a simple dimmer
the secret was the when we went for the installation we actually worked out all wrong earthing and loops rom the sound system and then of course our dimmer was absolutelly noisless .....
regards sierramike
sakis from east electronics informed me about this post and as his employe but also electrics engineer of the NTUA ( National Technical University of Athens )
i try to follow all the posts but is very strange that so many various opinions about the same issue and diferent aspects depending on the standards and the application ....
to me more or less makes no sense ....
many things are said here and some of them quiet strange i dlike to say ....
just a couple of things .....
audio systems ( maybe others like medical systems or tools or dut in a lab ) cannot be faced as electrical loads like other electrical loads like a bulb or a radiator ....
as sakis said there might be earth loops inside our home while we give power to a lighting system but those will not create audible noises ( or the noises created can not be herd)
the other thing is that you cannot treat audio systems with cortizone IE trying to supress noises or other related issues . you simply have to find what picks them up .......
to my opinion if our friend george had noise issues i would go for a solution like double T mains filters than an isolation trafo ... ( but thats my opinion ....only )
PS
sakis and me in our young times (18-20years old and some 20 years ago ) used to make a hell of a lot of money selling to clubs dimmers that produced zero noises to the audio system .....we produced a dimmer that had probabaly 5-6 componeds and was a hell of a simple dimmer
the secret was the when we went for the installation we actually worked out all wrong earthing and loops rom the sound system and then of course our dimmer was absolutelly noisless .....
regards sierramike
Re: well ....
I agree... Best to silience or shunt the noise at the source. But maybe in residential apts or condo can't do too much or too expensive to run a dedicated ckt. But sometimes the cheapest solution is a well implemented grounding scheme with a good isolation transformer (to power from an existing dirty ckt). Cheaper to run a single clean ground than a whole dedicated ckt.
sierramike said:
I agree... Best to silience or shunt the noise at the source. But maybe in residential apts or condo can't do too much or too expensive to run a dedicated ckt. But sometimes the cheapest solution is a well implemented grounding scheme with a good isolation transformer (to power from an existing dirty ckt). Cheaper to run a single clean ground than a whole dedicated ckt.
infinia said:
Tell you what. I've presented multiple code references. Those codes govern the entire electrical system, stopping at cord and plug connected equipment that is listed or approved for use (see post 35). Those codes are not my opinions, they are fact. They have stated, without exception, that 120V residential receptacles cannot float, but must be solidly grounded. You have presented your opinions about what is permitted, but have absolutely no proof.
Your challenge is to come up with ONE single code reference that permits you to float a power strip in a residential environment. That is what this thread has been debating from the start. Don't stray off into tangents about what works best, common mode noise, etc. You present illegal suggestions, and have not provided any citation that says otherwise. Sorry, a drawing without citing the source doesn't cut it.
Once you are inside a single cord and plug connected piece of equipment, fine.
If your response is "I don't care about the code", that's fine. But you can't say it's permitted; you have not proven it in the face of many references that say otherwise.
AndrewT said:
Don't know if we are talking about the same thing, but we use sensitive equipment in sloppy construction environments. Constantly tripping GFCI's because we apply test voltages from 1kV to 100kV to grounded equipment (insulation tests).
Solution is to use an isolation transformer to break this ground path. Yes, the secondary is bonded.
Is this what you are referring to? And if you are talking a construction/commercial/industrial environment, then a floating secondary may be possible. In the US, that would be covered by 29CFR-1910, or NFPA 70.
zigzagflux said:
That's what we are all talking about here from post one. But you to seem the view the world only from an electrical contractors or worse a building inspectors point of view. Instead of helping, your rather myopic posts IMO just keep on hindering and confusing the issue (ie GFCI). Read my first post in this thread.
Rather than dismissimg the diagram I posted (Did you even look at it) can't you comment on it's merits for clean power?
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